1. Field of the Invention
The present invention relates to an edge rinse mechanism, and more specifically to an edge rinse mechanism for removing only a peripheral portion of a resist film formed on a whole surface of a semiconductor wafer for a semiconductor device.
2. Description of Related Art
Referring to FIG. 1, there is shown a diagrammatic vertical sectional view of a prior art edge rinse mechanism incorporated in a resist deposition machine. This edge rinse mechanism is used for removing only a peripheral portion 2b of a resist film 2 deposited on the whole of a principal surface of a semiconductor wafer 1 so that a central portion 2a of the resist film 2 remains on the principal surface of the semiconductor wafer 1. Here, the central portion 2a of the resist film 2 corresponds to a resist pattern formation zone, and the peripheral portion 2b of the resist film 2 corresponds to a zone excluding the resist pattern formation zone.
In brief, the shown resist deposition machine includes a vacuum chuck 3a for sucking and holding the wafer 1 on an upper surface thereof. This vacuum chuck 3a is fixed to a vertical rotating shaft 3b, which is driven by a motor 3c, so that the chuck 3a and hence the wafer 1 are rotated by the motor 3c. The resist deposition machine also includes a cup 4 surrounding the chuck 3a and hence the wafer 1 held on the vacuum chuck 3a, separately from the wafer 1 held on the vacuum chuck 3a, and an exfoliating-agent discharging nozzle 5 directed to discharge a resist exfoliating agent 6 toward the peripheral portion 2b of the resist film 2 formed on the wafer 1 held on the vacuum chuck 3a.
In an edge rinsing operation of the above mentioned prior art edge rinse mechanism, the resist exfoliating agent 6 is discharged from the nozzle 5 while the wafer 1 which has the resist film 2 deposited on the whole principal surface thereof and which is sucked and held with the vacuum chuck 1, is rotated together with the vacuum chuck 1, so that only the peripheral portion 2b of the resist film 2 is dissolved, and on the other hand, the dissolved resist material and the resist exfoliating agent 6 are scattered radially outward from a periphery of the wafer 1 by action of a centrifugal force generated by the rotation of the wafer 1.
In this rinsing process, the scattered resist material and the scattered resist exfoliating agent 6 collide against an inner wall of the cup 4 and are bounded by the inner wall of the cup 4 so that, as designated with Reference Numeral "2c" in FIG. 2, the resist material and the resist exfoliating agent 6 adhere on the central portion 2a of the resist film 2, namely, the resist pattern formation zone, with the result that a concaveconvex is formed on an upper surface of the resist pattern formation zone 2a, which will cause a patterning defective.
Under the above mention circumstance, Japanese Patent Application Pre-examination Publication No. JP-A-01-214023, (the content of which is incorporated by reference in its entirety into this application, and also an English abstract of JP-A-01-214023 is available from the Japanese Patent Office and the content of the English abstract of JP-A-01-214023 is also incorporated by reference in its entirety into this application) proposes to locate a cylindrical cover to cover the resist pattern formation zone 2a from a position above the wafer 1, in order to prevent the scattered resist material and the scattered resist exfoliating agent 6 from adhering on the resist pattern formation zone 2a by action of the cylindrical cover. However, this approach is disadvantageous in that the resist material and the resist exfoliating agent 6 adhere and are piled up on the cylindrical cover. In addition, a drive mechanism for displacing and positioning the cylindrical cover is located directly above the resist pattern formation zone 2a. As a result, another problem is encountered in that the deposits on the cylindrical cover and dust generated from the drive mechanism will fall down and adhere on the resist pattern formation zone 2a.
In another proposed example, an inner cup having a number of small perforations is located at an inside of the cup 4, and is rotated at a high speed, so that by action of a centrifugal force, deposits such as the resist material deposited on the inner cup are caused to be scattered outward at the same time as the deposition, with the result that the material is prevented from being bounded to the resist pattern formation zone 2a by action of the inner cup. In this second proposal, however, if the resist material deposits on the rotating inner cup, the small perforations are clogged, so that a cup exhausting pressure and a wind speed vary, with the result that it becomes difficult to ceaselessly realize a uniform film thickness.